The present invention relates to video transmission apparatus and, more particularly, to apparatus for transmitting a plurality of video signals or audio signals, such as commercial messages (CMs), for broadcasting purposes.
It is known to transmit video or audio commercial messages for broadcasting purposes by utilizing a "cart" machine. The cart machine is an automatic cassette or disk changing and reproduction device which reproduces multiple recording media without manual loading of cassettes or disks. It also is known to record commercial messages on a cassette or disk in advance such that commercial messages previously recorded on several recording media can be reproduced and transmitted continuously and in a predetermined sequence without the need for human intervention to constantly exchange cassettes or disks.
Another system, shown in FIG. 1, is known to utilize a single backup video tape recorder to prevent periods of "dead air" when failures occur during reproduction or transmission of a commercial message or program. In this system, commercial messages stored on magnetic tapes in VCR 1, VCR 2, etc are copied (i.e. dubbed) onto a magnetic tape in a backup VCR in advance in a predetermined sequence by utilizing a switching circuit. During transmission, VCR 1, VCR 2, etc reproduce commercial messages in the predetermined sequence and at the same time, the backup VCR reproduces the same commercial messages such that should a failure occur in a VCR which is reproducing a commercial message, a switch selects the signal reproduced by the backup VCR, thus preventing periods of "dead air".
One problem encountered with these devices is that they are generally adapted for a single channel of reproduction and transmission and only have limited backup capability to deal with failures that may occur during signal reproduction or transmission.
Another difficulty encountered with the above described systems is their general inability to prevent periods of "dead air" without having only a single VCR reproduce or transmit commercial messages or programs at a time or without making copies of pre-recorded commercial messages or programs in advance when failures occur during reproduction or transmission. In addition, the preventive measure of having parallel systems and duplicate recording media containing the commercial messages generally is impractical due to added cost, size and complexity of such a system.